1. Field of the Invention
The present invention relates to an image processing apparatus and a control method thereof, which, as an instance, generate an image data that is printed with an electrophotographic printer.
2. Description of the Related Art
In recent times, a rapid adoption of color printing on the part of inkjet printers has been followed by a similar shift from black-and-white to color on the part of electrophotographic printer apparatuses, that is, copying machines or printers.
In general, electrophotographic printer apparatuses can be divided into two major types: a single drum type and a tandem type. A printer of the single drum type comprises a plurality of color developers in a periphery of an image carrier, that is, a photosensitive drum, wherein each respective developer supplies a toner of each respective color to form a color composite toner image upon the image carrier, and a color image is formed upon a sheet by transferring the color composite toner image. A printer of the tandem type, conversely, forms a toner image of a single color upon each of a plurality of image carriers, that is, photosensitive drums, that are installed in a side-by-side arrangement, and forms the color composite toner image upon the sheet that is conveyed by transferring each respective single color toner image upon the sheet in a sequence.
A comparison of the single drum type and the tandem type of printers reveals that the single drum type of printer has an advantage over the tandem type of printer, in that an image forming unit of the single type of printer can be made smaller, and is less expensive, than the tandem type of printer, owing to the fact that the single drum type of printer includes a single image carrier. On the other hand, the single drum type of printer is not suited to increasing performance speed, owing, again, to the fact that it employs the single image carrier to form the color image by repeating the image formation over a plurality of iterations. Conversely, while the tandem type of printer is inferior to the single drum type of printer with regard to the miniaturization and cost aspects, it is suited to increasing performance speed, owing to the fact that it is capable of performing the image forming independently for each respective color, and thus, it is possible to form the image in a single pass. Accordingly, in recent times, the tandem type of printer has attracted considerable attention with respect to the color printer, because it is possible to obtain an image forming speed thereby that is on a par with an image forming speed of a black-and-white printer.
With respect to the tandem type of printer, the color image is formed with the plurality of image carriers and a plurality of lasers, and it is accordingly desirable for a distance from each laser light source to each image carrier to be an equal distance in each instance. In actuality, however, a discrepancy in the scale between respective images that are formed thereby may arise as a result of such as a discrepancy in the distance from each respective laser light source to each respective corresponding image carrier, which may not be constant in every instance because of such as a mounting tolerance of each respective unit, or a discrepancy in the wavelength of each respective laser.
Conventionally, in order to compensate for the scaling discrepancy thereof, a method has been proposed that corrects a location of a lens of a laser optic system, or that varies a drive frequency of the laser. Furthermore, in recent times, a method has been proposed that corrects the discrepancy in the scale between each respective image by expanding or reducing the image by either introducing a pixel (hereinafter “supplemental pixel”) to the image, or deleting a pixel from the image, such as is disclosed in Japanese Patent No. 3,539,283.
With respect to a conventional tandem type of printer, the discrepancy in the distance from each respective laser light source to each respective corresponding image carrier is large, and as a consequence, the method is employed therein of corrects the location of the lens of the laser optic system, or that varies the drive frequency of the laser.
Such correction, however, employs an optical element such as an f-θ lens that is located between each respective laser light source and each respective corresponding image carrier, which, in addition, must be controlled with a high degree of precision. As a consequence, complex configuration and control are required, resulting in a comparatively more costly configuration.
Such as a dedicated LSI chip is also required when modulating the frequency, in which instance the cost would also increase.
In addition, Japanese Patent Application Laid Open No. 2000-238342 proposes another method for scale correction, wherein the scale correction is performed by introducing a blank pixel within one line of image data, in order to lengthen an image. Furthermore, in recent time, a printer is conceived of wherein the scale correction of an image is performed by segmenting a pixel of image data, and either inserting a segmented pixel (supplemental pixel) into the pixel, or else deleting a segmented pixel from the pixel.
When performing the scale correction by way of either such technique, however, the correction thereof extends only to the correction of the single line as a whole, in the main scanning direction, and does not take into account a lengthening or a contraction of the image in each respective region within the single line thereof, which may result from such as an optical characteristic thereof. As a consequence, a problem occurs wherein a degradation of the image may arise, owing to the lengthening or the contraction of the image in each respective region within the single line thereof.